This invention relates to a pump structure, particularly a fuel delivery pump including, in a unitary assembly, a pump proper and an electromotor and having a housing which is filled with the flow medium. The rotary armature of the electromotor is submerged in the flow medium which also serves as a lubricant for the bearings of the rotary components.
A pump of the aforenoted type, as disclosed, for example, in U.S. Pat. No. 3,259,072, comprises a housing which is made of a synthetic material and which is formed of a plurality of cylinders in an end-to-end arrangement. The electromotor is located in the cylindrical main portion of the housing. One side of the latter is bounded by a closure which contains the electric terminals and the support for the carbon brushes. To the other end of the housing there is attached a pump housing which is also made of a synthetic material and which has a diameter greater than that of the motor housing. The pump housing accommodates a centrifugal pump and has an inlet port and an outlet port. The motor chamber is filled with the flow medium of intermediate pressure through particular ports provided in the separating wall between the motor chamber and the pump chamber for lubricating the bearings and cooling the armature of the motor.
In the manufacture of the aforeoutlined pump, synthetic material is used to a significant extent. Since synthetic materials in general have only low strength values that are far below those of metallic parts, the components of this pump have to be of very substantial thickness resulting in a very bulky overall structure.